Consider a souce of sound `S`, and an observer/detector `D`. The source emits a sound wave of frequency `f_0`. The frequency observed by `D` is found to be (i) `f_1`, if `D` approaches `S` and `S` is stationary
(ii) `f_2`, if `S` approaches `S` and `S` is stationary
(iii) `f_3`,if both `S` and `D` and `D` is stationary Speed
In all three cases, relative velocity of `S` wrt `D` is the same. For this situation which is incorrect?

Options

A. `f_1nef_2nef_3`
B. `f_1ltf_2`
C. `f_3ltf_0`
D. `f_1ltf_3ltf_2`

Answer

B

Explanation

Let relative velocity of `v` and the speed of sound be `v_0`. Then,
`f_1=(v_0-(-v))/(v_0)xxf_0=(v_0+v)/(v_0)f_0`
`f_2=(v_0)/(v_0-v)xxf_0`
`f_3=(v_0+(v)/(2))/(v_0-(v)/(2))xxf_0`
It is clear from above that `f_1nef_2nef_3`,`f_3gtf_0` and we can prove that `f_2gtf_3gtf_1`.